Security constrained OPF by hybrid algorithms in interconnected power systems

This paper presents a hybrid algorithin for solving security constrained OPF in interconnected power systems, which is based on the combined application of evolutionary programming (EP) and sequential quadratic programming (SQP). The efficient algorithm combining main advantages of two methods is as follows: Firstly, EP is applied to perform global exploitation among a population, This gives a good initial point of conventional method, Then, SQP are used to perform local exploitation. The hybrid approach often outperforms each method operating alone and reduces the total computation time. The objective functions are the minimization of generation fuel costs and system power losses. In OPF considering security, the outages are selected by contingency ranking method, The control variables are the active power of the generating units, the voltage magnitude of the generator, transformer tap settings and SVC setting. The state variables are the bus voltage magnitude, the reactive power of the generating unit, line flows and the tie line flow. The method proposed is applied to the modified IEEE model system,